Orthogonal frequency division multiplexing (OFDM) is a multi-carrier transmission technique in which a user transmits on many orthogonal frequencies (or carriers). The orthogonal carriers are individually modulated and closely spaced, but have minimal interference with one another. This provides high spectral efficiency and resistance to multipath effects. An orthogonal frequency division multiple access (OFDMA) system allows carriers (or sets of sub-carriers) in a subject frequency band to be assigned to different users concurrently, rather than to a single user. Today, OFDM transmission technique is used in both wireline transmission systems and wireless transmission systems. OFDM and OFDMA techniques are also used for wireless digital audio and video broadcasting.
However, conventional OFDM/OFDMA networks may not fully and efficiently utilize the full bandwidth allocated or available to a base station in a wireless network. In particular, OFDM/OFDMA networks do not efficiently utilize the spacing between frequency channels, in the available bandwidth of a given spectrum block.
Therefore, there is a need in the art for improving the spectrum usage efficiency of orthogonal frequency division multiplexing (OFDM) transmission systems and/or orthogonal frequency division multiple access (OFDMA) transmission systems, especially in the scenario of deploying multiple, adjacent OFDM channels.